Our goal is to construct a "mini" rDNA gene containing about 100 mucleotides to the left of the first transcribed nucleotide and about 100 bases down-stream. To this fragment we will fuse an approximately 200 bp fragment containing the termination codon. This gene will be used for transcription studies. To this end our immediate goal is to determine the RNA sequence at the 5' and 3' end of the 45S primary rRNA transcript and to align these sequences with sequences on recombinant plasmids containing mouse rDNA.